It is in the rotor. If one takes the front panel off of the generator head there will be a small terminal strip. This carries a signal from the regulator to a small stator which is visible (barely) with the panel off.
That signal to the stator causes an AC voltage to be developed in the end of the rotor. The bridge rectifier in the rotor converts that AC signal to a DC signal with in turn excites the main AC generator.
The generator head actually has three generators inside of it. First is the generator that makes the AC that powers the voltage regulator (quad winding).
Second is the generator above that takes the output of the regulator and converts it to AC which is in then converted to DC (using the bridge) to excite the main generator.
Third is the main generator that actually makes the AC that is the output of the unit..
The diodes are encased in plastic and are two half-moon pieces. They look identical, but they ARE NOT. Since they are potted in plastic, they come out as two units "+" and "-". If you remove them, be sure to mark them as to which one came from where.
Supposedly one should be able to test the diodes without removing the generator end, but I don't see how that could be done. Replacing the diodes would mean replacing both of the potted diode units.
It would be relatively easy if 1) you had a good set of replacement diodes 2)you had the entire front section of the generator removed as well as the front frame of the generator head and 3) if you were double and triple sure that you marked which potted unit came out of which position on the rotor. Once out, the potted units are marked as to whether they are "+" or "-", but I'm not sure you can read that until the potted units are removed.
Potted units are held in with simple screws, so once you it all taken apart to get that far, removal is "simple".
Just by the way --- the use of that separate exciter rotor / bridge rectifier / exciter stator is the only way that the manufacturer can make a 'brushless' generator. It may seem complicated, but ya gotta get that regulator signal that is stationary into that rotor which is moving somehow.
z
